1. Field of the Invention
This invention relates generally to the field of surgery and more particularly to iris retracting instruments for use in ophthalmic surgery.
2. Description of the Prior Art
A number of instruments have been developed for use as iris retractors in ophthalmic surgery. These instruments generally are identified by the name of their developer and are commercially available. These include the iris retractors of Spivey, Bronson-Turtz, Rosenbaum-Drews, and Rizzuti. All of the above identified instruments are unitary hook or blade-type structures.
Such devices frequently have a number of disadvantages; for one, retraction of the iris is along one vector only, secondly they are frequently difficult to insert and remove; thirdly, they are generally unable to alter the attained pupillary size under different operative conditions; fourthly, they are generally unable to place simultaneous pressure during iris retraction on the posterior edge of the corneal wound to aid in expression of the lens; and fifthly, application at specific points of excessive force on the iris sphincter can damage this structure.
Another instrument designed for this purpose is the Eisner speculum. This speculum includes a pair of relatively large curved blades mounted on a tweezers-like structure that is outwardly spring-biased. The curved tips do not provide adequate positively engaging surfaces for engaging the iris nor is the outward movement or expansion of the tips limited except by the manipulation of the operator and the outermost spring expansion limit. The size of Eisner's tips or blades do not permit easy insertion into the pupil and they lack adequate iris grasping capability. The fact that the blades of Eisner fail to have a lower lip for engaging the iris requires that the surgeon maintain pressure with the instrument on the anterior surface of the lens. If this downward pressure is relaxed temporarily, one or more of the blades can be disengaged and the pupil collapsed at a critical time. In addition, Eisner's retracting blades have discrete front and back edges which can cause excess force to be exerted at discrete points on the iris sphincter and to cause injury at these points. The design of Eisner's handle makes it necessary for the surgeon to manipulate the instrument with his hand held in an uncomfortable and awkward mid-line position. In manipulating Eisner's instrument, the separation of the blades is achieved by relaxation of the grip pressure on the handle. Relaxation of this pressure also loosens the operator's grip on the instrument and makes precise manipulation difficult. The design of Eisener's blades prohibits the application of pressure on the posterior lip of the corneal incision so that pressure cannot be simultaneously exerted to facilitate lens expression and extraction. An instrument similar to the Eisner speculum but designed for use in performing spinal fusion is the Spreader Instrument of Peterson shown in Pat. No. 3,916,907.
A number of other instruments for use in eye surgery have also been described in the patent art. These include the patent to Suffa entitled "Speculum" U.S. Pat. No. 1,237,121 and the patent to Pulliam entitled "Eye Speculum" U.S. Pat. No. 2,438,646. Both of these inventions are intended to be used for separating the eye lids of a patient and are not designed for retraction of the iris.
Additional patents specifically designed for use in iris retraction are the Surgical Device of Illig. U.S. Pat. No. 3,490,455 and the Ocular Surgical System of McReynolds, U.S. Pat. No. 4,037,589. The device of Illig is an iris engaging hook 12 and is designed to be sutured to the sclera of the eye. A considerable amount of time is involved in the placement and removal of the devices of Illig and, if used in conjunction with crystalline lens removal, may permit the escape of vitreous humor through the pupil because of the time delay involved in its removal from the eye.
The system of McReynolds employs a speculum frame for maintaining the eyelids apart and a plurality of wire hooks which engage the iris to separate the iris outwardly. As was true for the Illig device, the placement and removal of the hooks require an undue amount of time operative risk.